The second messenger inositol 1,4,5-trisphosphate (IP3) regulates intracellular calcium signals through IP3 receptors (IP3Rs). This pathway is central to a wide range of cellular processes. However the functions of IP3R mediated signalling in the biology of whole animals have been rather poorly understood. Recent studies in C. elegans have identified a range of functions in the development, behaviour and physiology of hermaphrodites. IP3Rs in C. elegans are encoded by a single gene,
itr-1. It has been shown that
itr-1 participates in the control of ovulation1 and defecation2. In addition we have shown that IP3-mediated signalling is important in multiple events during embryogenesis and in the regulation of pharyngeal pumping in response to food3. To develop a fuller understanding of the range of functions of
itr-1 in C. elegans we investigated its roles in the biology of males. Itr-1 has three promoters (pA, pB, pC), each of which directs expression in a different and specific set of cells in hermaphrodites4,5. Promoter GFP fusions were crossed into a
him-8 background and the expression pattern for each promoter was determined. The three promoters gave different expression patterns, which included male specific structures. RNAi by feeding has been used to characterise the function of
itr-1 in hermaphrodites3. We carried out RNAi on
itr-1 in males and demonstrated that IP3R function in pharyngeal pumping and defecation are conserved. We also observed a severe reduction in male fertility in
itr-1 RNAi males. Male mating behaviour was examined, turning, vulva location and spicule insertion were scored. RNAi males show an increase in number of "sloppy" turns. We also examined sperm transfer and discovered that RNAi males transfer less sperm than wild type males. However fertility assays suggest that these alterations are insufficient to account for the observed decrease in offspring. Thus in
itr-1 knock-down animals the ability for sperm to fertilise may also be reduced.